Tuberculosis Dosing for Adolescents (12-18 Years)
For adolescents aged 12-18 years, use adult dosing regimens when they weigh ≥40 kg or are ≥15 years old; otherwise, use pediatric weight-based dosing with the same four-drug regimen. 1
Dosing Algorithm by Age and Weight
Adolescents ≥15 years OR ≥40 kg: Use Adult Doses
- Isoniazid: 5 mg/kg daily (maximum 300 mg) 1, 2, 3
- Rifampin: 10 mg/kg daily (maximum 600 mg) 1, 2, 3
- Pyrazinamide: 15-30 mg/kg daily (maximum 2000 mg) 1, 2, 4
- Ethambutol: 15-25 mg/kg daily (maximum 2500 mg) 1, 2, 3
Adolescents 12-14 years AND <40 kg: Use Pediatric Doses
- Isoniazid: 10-15 mg/kg daily (maximum 300 mg) 1, 2, 5
- Rifampin: 10-20 mg/kg daily (maximum 600 mg) 1, 2, 3
- Pyrazinamide: 35 mg/kg (range 30-40 mg/kg) daily (maximum 2000 mg) 1, 2
- Ethambutol: 20 mg/kg (range 15-25 mg/kg) daily (maximum 2500 mg) 1, 2
Treatment Regimen: No Change from Adults
The standard 6-month regimen remains unchanged for adolescents with drug-susceptible tuberculosis. 1, 6
Intensive Phase (First 2 Months)
- All four drugs daily: Isoniazid + Rifampin + Pyrazinamide + Ethambutol 1, 6
- Duration: 8 weeks (56 doses) 1, 5
Continuation Phase (Next 4 Months)
- Two drugs daily: Isoniazid + Rifampin 1, 6
- Duration: 18 weeks (126 doses) 1, 5
- Total treatment duration: 6 months for drug-susceptible pulmonary TB 1, 6
Critical Dosing Considerations
Pyridoxine Supplementation
- Give pyridoxine 25-50 mg daily to all adolescents receiving isoniazid who have risk factors including HIV infection, diabetes, malnutrition, or pregnancy 1, 2, 7
Weight-Based Dosing Principles
- Use actual body weight for non-obese patients 1, 2
- For obese adolescents (>20% above ideal body weight), consider using ideal body weight or modified ideal body weight for initial dosing 1
Monitoring Requirements
- Baseline liver function tests before starting therapy 7
- Monthly monitoring for hepatotoxicity during the first 2 months 7
- Visual acuity monitoring if using ethambutol (baseline and monthly) 1
- Directly observed therapy (DOT) is recommended for all adolescents 7, 5
Common Pitfalls to Avoid
Age vs. Weight Confusion
The guideline explicitly states that adult dosing begins at age 15 years OR at weight >40 kg in younger children, whichever comes first 1. Do not automatically use pediatric dosing for all patients under 18 years.
Ethambutol in Younger Adolescents
While ethambutol can be used in adolescents 12-18 years, ensure visual acuity can be reliably monitored 1. If monitoring is not feasible in younger adolescents with low drug resistance risk, consider a three-drug regimen after consultation with TB experts 1.
Intermittent Dosing
If using twice-weekly or thrice-weekly regimens (not recommended as first-line), doses differ significantly: isoniazid increases to 15 mg/kg (max 900 mg), pyrazinamide to 50 mg/kg, and ethambutol to 50 mg/kg 1, 2, 4. However, daily therapy is preferred for adolescents 1.
HIV Co-infection
Adolescents with HIV may require longer treatment duration (up to 9 months) and closer monitoring for malabsorption 5, 6. Drug-drug interactions with antiretroviral therapy must be considered, particularly with rifampin 3.